1. Field of the Invention
The present invention relates to a solid-state imaging device and a method of producing a solid-state imaging device. In particular, the present invention relates to a solid-state imaging device in which an interface state of a surface of a semiconductor substrate having a sensor that performs photoelectric conversion can be compensated for.
2. Description of the Related Art
It is known that, in a solid-state imaging device such as a CCD or CMOS image sensor, crystal defects in the sensor composed of a photodiode and an interface state at an interface between a surface of the sensor and a film disposed thereon become causes of generation of dark current. A hole accumulated diode (HAD) structure is known as a technology for suppressing the generation of dark current due to the interface state, which is one of the above causes.
FIG. 8A shows a structure to which the HAD structure is not applied. In the structure shown in FIG. 8A, the upper portion of a sensor 203 formed on a surface side of a semiconductor substrate 201 is directly covered with an insulating film 205. Consequently, electrons generated due to an interface state formed at an interface between the sensor 203 and the insulating film 205 flow in the sensor 203 in the form of dark current. In contrast, FIG. 8B shows a structure to which the HAD structure is applied. In the structure shown in FIG. 8B, a hole accumulation layer 207 composed of a P-type diffusion layer is provided on a sensor 203 to cover a surface of a semiconductor substrate 201, and an insulating film 205 is provided on the hole accumulation layer 207. Consequently, electrons generated due to an interface state between the hole accumulation layer 207 constituting the surface of the semiconductor substrate and the insulating film 205 disappear in the hole accumulation layer 207, thus preventing generation of dark current.
Such an HAD structure described above can be used in either a CCD image sensor or a CMOS image sensor. Furthermore, the HAD structure can be applied not only to a surface irradiation-type image sensor in the related art but also to a rear-surface irradiation-type image sensor (refer to, for example, Japanese Unexamined Patent Application Publication No. 2003-338615).